To rename the start button, you will need a hex editor.
My preference is UltraEdit

1. Copy the \windows\explore.exe file to a new name (e.g. explorer_1.exe)
2. With the hex editor, open that file and go to offset 412b6
3. You will see the word start with blanks between each letter
4. Edit it be any 5 characters or less
5. Save the file
6. Boot to DOS
7. Copy the existing c:\windows\explorer.exe to explorer.org
8. Copy explorer_1.exe to explorer.exe
9. You will also need to replace the explorer.exe in the c:\windows\system32\dllcache file as well with the new one.

Note: If the partition is NTFS and you can't access the files from DOS: